> From: Ma, WenwuX [mailto:wenwux...@intel.com] > Sent: Tuesday, 27 September 2022 09.32 > > > From: Morten Brørup <m...@smartsharesystems.com> > > Sent: 2022年9月7日 22:47 > > > > > From: Wenwu Ma [mailto:wenwux...@intel.com] > > > Sent: Monday, 29 August 2022 02.57 > > > > > > Offloading small packets to DMA degrades throughput 10%~20%, and > this > > > is because DMA offloading is not free and DMA is not good at > > > processing small packets. In addition, control plane packets are > > > usually small, and assign those packets to DMA will significantly > > > increase latency, which may cause timeout like TCP handshake > packets. > > > Therefore, this patch use CPU to perform small copies in vhost. > > > > > > Signed-off-by: Wenwu Ma <wenwux...@intel.com> > > > --- > > > > [...] > > > > > diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c index > > > 35fa4670fd..cf796183a0 100644 > > > --- a/lib/vhost/virtio_net.c > > > +++ b/lib/vhost/virtio_net.c > > > @@ -26,6 +26,8 @@ > > > > > > #define MAX_BATCH_LEN 256 > > > > > > +#define CPU_COPY_THRESHOLD_LEN 256 > > > > This threshold may not be optimal for all CPU architectures and/or > DMA > > engines. > > > > Could you please provide a test application to compare the > performance of > > DMA copy with CPU rte_memcpy? > > > > The performance metric should be simple: How many cycles does the CPU > > spend copying various packet sizes using each the two methods. > > > > You could provide test_dmadev_perf.c in addition to the existing > > test_dmadev.c. > > You can probably copy a some of the concepts and code from > > test_memcpy_perf.c. > > Alternatively, you might be able to add DMA copy to > test_memcpy_perf.c. > > > > I'm sorry to push this on you - it should have been done as part of > DMAdev > > development already. > > > > -Morten > > The test application has been supported by the following patch. > > http://patchwork.dpdk.org/project/dpdk/patch/20220919113957.52127-1- > cheng1.ji...@intel.com/ >
Yes, thank you for reminding me. Acked-by: Morten Brørup <m...@smartsharesystems.com>
